Thanks Parak.
Yep, did the USB reinforce already.
The bit that has me about the way the behavior has been is that I installed the LEDs on the switches before any soldering took place. In other words, I pulled the switches apart en'masse to put the SIPs in, then put the LEDs in. After all that, I started populating the plate & pcb with the completed switches. So the fact that both halves behave in exactly the same way when the switches were loaded in a completely random fashion (with regard to LED placement) had me scratching my head.
I have yet to keep working with the board this weekend, but dying to get it finished.